Integer and fractional part of the number

Question

Hello everybody,
I want to divide the floating point number to 2 integer words, first will receive the interger part of number, and the second will receive the fractional part of the number.
For example: I have number 751.98 in DBL, then I create two integer fields: first has value 751, second has value 98.
I have tried simple conversion from DBL to I16, but it always rounded me to higher interger. I don't want to round it. And I just don't know how to transform the fractional part to integer. Are there any specialized functions for this? Maybe should I use log10 or similar?
TIA,
Jacek.

Answer 1

The place to start with this problem is the IEEE-754 numerical
representations:
32 bit floating point is internally:
highest order bit is the sign bit.
the next 8 bits are the exponent bits
the last 23 bits are the mantissa bits
the mantissas and exponents are binary.
the mantissa value in a 1.22 fixed point binary number, i.e. the most
significant binary bit is equal to 1, the next most is equal to 1/2,
the next most is equal to 1/4, etc., etc.
The exponent part can go between 2^-127 and 2^128
You should be able to cast your 32 bit float to a 32 bit unsigned
integer, separate it into sign, mantissa and exponent parts, use the
exponent to rotate left or right your mantissa decimal point by the
exponent value and then separate the whole part from the fractional
part and then put each into the I16's or U16's as you want.
Douglas De Clue
LabVIEW programmer
[email protected]
[email protected] (Michael Ross) wrote in message news:...
> This problem needs some limits. Like: only return the decimal portion
> out to 6 places.
>
> First run the number through Remainder and Quotient (divisor of 1).
>
> 751.98743674645641000000 gets remainder of
>
> 0.98743674645641021900
>
> "floor" is 751
>
> Take the remainder and send through Decimal to Fractional String (this
> is where you set your number of decimal places [default is 6]).
>
> returns 0.987437
>
> Then use String Subset and set it to an offset of 2 (cleans off the
> leading zero and decimal point) with the "length" input left at the
> default of "rest" (of string).
>
> 987437 (in string form)
>
> Now use String to Decimal Number
>
> returns 987437 (as a decimal number)
> ====================================
> I think if you don't limit the number of places it is ugly. It is
> ugly going from numbers to strings and then back. But all numbers is a
> bad thing.
>
> The alogirithm for finding the answer mathematically is nasty.
> Especially without a limit on decimal places. You have to figure out
> the number of decimal places and multiply by the inverse of the last
> decimal place. Sounds easy.
> =============================
> Try this: New number: 751.98652
>
> Truncate out the remainder (Remainder and Quotient (divisor of 1)):
>
> 751.98652 ---> 0.98652
>
> Mult by 10 ----> 9.8652
>
> Take the floor (9) and divide by 10 ----> 0.9
>
> subtract the new number from the old. Is the answer non-zero? Not,
> then keep on
>
> 0.98652 - 0.9 = .08652 which not equal to 0
>
> If it is zero, the floor is the answer.
>
> Continue - Not:
>
> This time multiply by 100 ----> 98.652
>
> floor is 98, divide by 100 ----> 0.98
>
> Subtract 0.98 from 0.98652 = .00652 still non zero.
>
> Keep on. 1,000, 10,000...When you get to 100,000
>
> 0.98652 x 100,000 = 98652.00
>
> Get the floor
>
> divide the floor by 100,000 to get the original number (remainder is
> now 0.000), compare to original remainder
>
> 0.98652 - 0.98652 = 0. Yay.
>
> Take the 98652 and go with it. The last place was the one hundred
> thousandth.
>
> I can't take credit for the last, I had uglier stuff going on. I did
> do the string thing.
>
> I swear this is just like some sorry homework problem.
>
> Mike